A bill before the New Mexico House would allow for mines in the state to suspend operations but remain on standby for up to 100 years and reopen at any time without public notice.

House Bill 625 has been before the the House Energy, Environment and Natural Resources Committee twice before. It is sponsored by Rep. John Zimmerman, R-Las Cruces and supported by the mining industry in the state, the Santa Fe New Mexican reported.

Opponents say the bill weakens critical parts of the Mining Act that protects the public and groundwater from pollution.

A legislative analysis noted that some of the proposed changes in the bill would clarify the law’s requirements for mining companies.

But a provision that would remove a cap on the number of years a mine can remain on standby would be a big concern for Grant County and the Silver City area, which is near two open-pit copper mines that cover thousands of acres — some of the largest in the nation.

Currently, a mine can remain on standby for five years at a time, up to 20 years. At the end of each five-year term, the company can request to extend the period. If a company wants to reopen a mine, the Mining and Minerals Division and the public must be notified, and a hearing must held to determine if any changes are needed to the original mine operation permit.

Under HB 625, a mine could essentially remain on standby for at least 100 years. If at any time a mine’s operators wanted to reopen, they would need only alert the state in a letter. No public review of the request or the mine’s operating permit would be required under the bill.

Mines that are on standby don’t have to be reclaimed and restored to a more natural state. Critics see the bill’s provision as granting mining companies permission to avoid the expense of cleaning up and shutting down a mine.

Allyson Siwik, director of the Gila Resources Information Project said the bill also removes a provision of the Mining Act that requires a company that closes a mine to ensure that the site is reclaimed in such a way that it never presents a threat to groundwater and meets environmental standards. If an older openpit mine, like Freeport McMoRan’s copper mine near Silver City, closed now, it would have to continually pump out water collecting in the pits and treat it to prevent contamination from seeping into groundwater. The act encourages new mines to be designed in such a way that they won’t require continual care after they are closed.

Under HB 625, a company wouldn’t have to design new mines to avoid long-term pollution and wouldn’t have to provide for the perpetual care of a closed mine site.

The bill has been revised a couple of times.

New Mexico has more than 500 mines to extract resources such as copper, coal, potash and aggregates. The state is 13th in the United States in coal production, fourth in copper and first in potash. The mining industry, not including oil and gas, employed about 4,600 people directly and 11,000 indirectly in 2013, according to a report from New Mexico Department of Workforce Solutions. In 2012, mining generated $43 million in revenues to the state.